Description:
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When using server-side prepared statements, MySQL errors happening during execution are not returned by PDO MySQL.

This happens in PHP 5.6 and PHP 7.0.

Test script:
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$p = new PDO('mysql:host=localhost;charset=utf8', 'root', '', array(PDO::MYSQL_ATTR_COMPRESS => false));

$p->setAttribute(PDO::ATTR_EMULATE_PREPARES, false); // server

$p->query('CREATE DATABASE IF NOT EXISTS fixture');
$p->query('DROP TABLE IF EXISTS fixture.MysqlDatabaseTest');
$p->query('CREATE TABLE fixture.MysqlDatabaseTest (MysqlDatabaseTest_id INT NOT NULL AUTO_INCREMENT PRIMARY KEY, i INT NOT NULL) ENGINE=MyISAM');
$p->query('INSERT INTO fixture.MysqlDatabaseTest SET i = 1');
$p->query('INSERT INTO fixture.MysqlDatabaseTest SET i = 42');

$s = $p->prepare('SELECT i FROM fixture.MysqlDatabaseTest WHERE i = (SELECT i FROM fixture.MysqlDatabaseTest)');

$success = $s ? $s->execute() : null;;

var_dump($success, $s, $p->errorInfo());
if ($s)
	var_dump($s->errorInfo(), $s->fetchAll());


Expected result:
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Error: Subquery returns more than 1 row

Actual result:
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No error, `$s->fetchAll()` returns an empty result array.